1. Field of the Invention
The present invention relates to a hydraulic braking system and in particular to a hydraulic braking system in which a tandem master cylinder and an anti-skid device are combined.
2. Description of the Prior Art
Generally speaking, in a hydraulic braking system of that kind, first and second pressure chambers arranged in a tandem master cylinder are in fluid communication with first and second sets of wheel cylinders, respectively. In order to define both chambers in a bore formed in a body of the tandem master cylinder, a first piston and a second piston, both of which are slidably fitted in the bore, are operatively connected with each other in series so as to be moved by a brake pedal. Since the pressures in both chambers are decreased during the actuation of an anti-skid device, the brake pedal is undesirably subject to move in the direction of the depression.
For preventing such a drawback, U.S. Pat. No. 4,729,610 discloses a sleeve which is slidably mounted on a first piston so as to be brought into engagement with a pedal operated booster piston. However, with a view to preventing the generation of noise and/or shock upon the above-mentioned engagement, and additional means has to be provided. That is to say, an annular gap in which fluid is filled is defined between the sleeve and a bore. During movement of the sleeve towards the booster piston, fluid is discharged from the annular gap through an orifice formed radially in the sleeve. Thus, the movement of the sleeve is decelerated with the result that an abrupt engagement of the sleeve with the boost piston is avoided.
However, it is cumbersome to provide such additional means including the annular gap. Also, due to such additional means, the tandem master cylinder becomes complex in construction. Further, upon loading of the orifice, the additional means or deaccelerating means is brought into malfunction.